Hydroxyisocaproic acid is an end product of leucine metabolism in human tissues such as muscle and connective tissue. It belongs to 2-hydroxycarboxylic acid group of amino acid metabolites (PMID 6434570 ). Hydroxyisocaproic acid functions as an “anti-catabolite” and is widely used in the body building community. Chronic alpha-hydroxyisocaproic acid treatment of rats has been shown to improve muscle recovery after immobilization-induced atrophy (PMID: 23757407 ). Additionally, a 4-week hydroxyisocaproic acid supplementation of 1.5 g a day was shown to lead to increases in muscle mass during an intensive training period among soccer athletes (PMID: 20051111 ). Hydroxyisocaproic acid has also shown some potential as a topical antibiotic (PMID: 22483561 ). Elevated levels of 2-hydroxyisocaproic acid have been found in the urine of patients with dihydrolipoyl dehydrogenase (E3) deficiency (PMID: 6688766 ). Hydroxyisocaproic acid is also elevated in maple syrup urine disease, a genetic disorder, and has been shown to accelerate lipid peroxidation. It may also be an indicator of oxidative stress (PMID: 11894849 ).